Blade ring for radial flow elastic fluid turbines



Nov. 10, 1931. E. o. ERI KSSON ET AL 1,331,104

BLADE RING FOR RADIAL'FLOW ELASTIC FLUID TURBINES Filed Oct, 15, 1928 2 Sheets-Sheet l 6 Z359? /5 l /0 /e w ImI/enfins: J5 M 0% MW Nov. 10, 1931. E. o. ERIKSSON ET AL 1,831,104

BLADE RING FOR RADIAL FLOW ELASTIC FLUID TURBINES Filed on. 15. 1928 I 2 Sheets-Sheet 2 Invenhris Patented Nov. 10, 1931 v UNITED STATES ERIK oT'rov ERIKSSON, or mnmeo, swnnnn, Ann GUSTAV Nonnen N, or LONDON;

mm OFFICE 1 ENGLAND, ASSIGNORS 'i'o AKTIEBOLAGET- LJUNGSTROMS ANGTURBIN', on srocx HOLM, SWEDEN, A JOINT-STOCK COMPANY OF SWEDEN BLADE RING non RADIAL snow ELASTIC FLUID TURBINEs Application filed October 13, 1928, Serial :No. 312,233, and in Sweden October 15, 1927.

The present invention relates to blade rings for radial flow elastic fluid turbines and has particular reference to improvements in theconstruction of such rings for turbines of the so-called Ljungstrom type.

The blade rings of turbines of the above type consist of two or more annular axially spaced ringbonds with a plurality of blades secured between them, the several blade rings employed in a, turbine being of different diameters and telescoped' so as to provide a radial path of flow for the motive fluid through the blading.

In accordance with earlier forms of cone struct'ion the turbine blades have been out from lengths of profiled blank material and have had their ends fitted in holes of corresponding form provided in sheet metal rings, the blades being welded to the rings to provide a blade'ring of generally cylindrical form. Projecting edges of dovetail section have then been formed on the sides of said ring, these edges'then being fitted into correspondingannularslots or grooves in annular ring bondswith which they have been united to form a rigid unit by rolling or otherwise forcing the edges of the grooves in t'hering bonds over the dovetail projections on the ring portions. The above described method of'manufacture involves a number of serious disadvantages. method is apoor one from an economical standpoint since it is necessary to provide various special auxiliary means to insure the proper positioning of the blades during the welding process. Furthermore the necessary heat treatment has an adverse affect on the durability of the material and also sets up stresses which tend to warp the blade rings and render diflicult the production of blade rings which moi proper shape after being cooled subsequent to the welding'operation.

It has been suggested, therefore, to make the blades out of a blank by milling the same, or by making the same in some other suitable manner so that two thicker end portions would be left on each "plate, 'which' portions would both be provided with dove-tail projections adapted to be fit'ted into'c'orrespondingly' shaped annular grooves provided in the In the first place thering bonds connected With said end portions widthrequired by the pitch. Otherwise, the

ring produced by the dove=tail portions of the blades will become uneven, 'or the blades will not entirely fill the annular slot :or groove inwhich they are to be secured.

The general object of the present invention is to improve upon prior forms of blade ring construction and the manner in which this and the more detailed objects of the invention are attained may best be understood from the following description of the several examples ofblade ring construction illustrated in the accompanying drawings forming a part of this specification.

Fig. 1 shows a cross-section of a radial flow elastic fluid turbine having blade rings rotating in opposite directions. Fig.2 shows a section on an enlarged scale of a blade ring embodying the invention. Fig. 3 shows the same blade ring viewed from above. Fig. 41- shows a section of a blade ring on line 1-4 m Fig. 2. blade ring on line 5+5 in Fig. 4;, Figs. 6 and 7 illustrate other forms of ring bonds for carrying the invention into effect.

Fig. 5 shows a section of a In Fig. 1, the center line 1 designatesth e axis "of rotation of the turbine shaft-2, and the section line 3 indicates a plane with respect to which the blading of the turbine is axially symmetrical. The turbine illustrat ed comprises'it'our blade systems 4, 5,6 and 7. The {motive fluid entering the turbine through the channel 8 flows through the above blade systems in the order named and gives-upits-energy to the bladerin'gs, of which alternate blade rings rotate in opposite directions. 4 I I Figs. -2- and"3 illustrate a blade ring having a plurality of blades: 10 each otwhich V lS ShflipQCl at its ends to provide heads 13 and 14, these heads being fitted respectively into grooves 13a and 14a in the respective r ng bonds and 16. These grooves open axially inwardly of the ring bonds and extend from the radially inner faces thereof in a generally radial direction partially through the material of the ring bonds, to form what may be termed blade retaining pockets.

In the example illustrated the part of the turbine rotor to which the blade ring is attached is indicated at 21 and the ring is at tached thereto bymeans of an articulated expansion ring 22 oining the parts 16 and 21.

In the present embodiment the end portions 13 and let of the blades are of dovetail form in peripheral section and the grooves 13a and lea are of complementary dovetail form as will be seen from Fig. 5, and as will be evident from Fig. 3 which shows in dotted lines the end portions of one of the blades 10, theseend portions substantially fill the pockets provided by the grooves 13a and 14:66., As will be seen from Fig. 4: the grooves 13a and lea are circumferentially spaced so that each blade is independently mounted between the ring bonds and any inaccuracy in the positioning of one blade will in no wise affect the accurate positioning of any other blade in the blade ring. The grooves 13a and 14a are advantageously formed by means of an end mill and the end portions of the blades are inserted in the pockets from the radially inner sides 'of the ring bonds. It will be observed that the grooves in the ring bonds which extend radially only partially through the material of the bonds, leave-a full section of metal as at 12 (Fig. 9) at the outer peripheral portion of the ring bonds.

Due to the thickened end portions of the blades which in the present embodiment are of dovetail. form, the blade ring is firmly held together as a unit against axial stresses tending to pull the blades from the ring bonds and when the turbine is in operation the centrifugal force acting onthe blades holds them firmly in position in radial direction. 7

Due to the type of fastening each blade may be considered independently as a beam fixed at both ends and with respect to the forces acting thereon due to rotation of the blade rings, the calculations for the blades may readily be made on the above basis.

In order to prevent any possibility of a blade becoming dislodged from the ring bonds when not held in radial position by centrifugal force, it is preferable to provide means for locking the blade ends in their respective pockets. On the ring bond 15 in Fig. 2 one means of locking the blades is illustrated, this means comprising a groove 17 on the radially-inner face of the ring bond adjacent to the bottoms of grooves 13a. This circumferential groove provides a flange 18 respect to the radius.

which may be readily beaded over the ends 13 of the blades after they are inserted.

The ring bond 16 illustrates another means for locking the blades in position. In this instance the end portion 1 1 of the blade has less radial depth than the pocket 140;, thus permitting one or more of the edges of the I blade retaining pocket to bebeaded over the end portion of the blade as shown at 20.

The grooves 13a and 14a intended for each blade may be milled out either radially or, as shown in Fig. 1, somewhat obliquely with In the latter case, the dove-tail portions of the blades,'and thus also the grooves, extend preferably in or approximately in the direction of one moment axis of the blade. The dove-tail part will then be longer, which results in a stronger attachment. Also, less material is required in a blade made in this manner.

Figs. 6 and 7 illustrate further forms of pockets in the ring bonds by means of which the blades can be secured in accordance with the present invention. In the embodiment shown in Fig. 6 the pockets 13b are rectangular in section and open toward the axially inner face of the ring bond '15 through necks of less circumferential extent than the main body of the grooves. V In the embodimentillustrated in Fig. 7 the grooves 180 are circular in section rather than rectangular as in the embodiment shown in Fig. 6 and likewise'have relatively narrow necks providing openings between the main portions of the grooves and the axially inner face of the'ring bond. 7

From the foregoing descriptions it will be evident thatthe invention is not dependent upon the specific shape of the endportions of the blades and the form of the pockets in which they seat. Various shapes of blade ends other than those illustrated may be employed. The essential feature of the invention is the independent mounting of the 7 blades in separate grooves so that the blades may be separately manufactured and assembled and so that accurate positioning of an one blade in the blade ring will not be dependent upon the accuracy in manufacture or assembly of other blades therein.

by Letters Patent of the United States of America is:

1. A blade ring for radial flow elastic fluid turbines comprising two axially spaced ring .bonds having a plurality of separate circumferentially spaced grooves opening axially inwardly and extending from the radially inner faces of the bonds in a generally radial direction partially through the material of the bonds to form blade retaining pockets, and a plurality of blades having end portions seated in said pockets, there being a separate pocket for each end portion of each blade and each of said end portions substantially filling out a separate pocket.

2. A blade ring for radial flow elastic fluid turbines comprising two axially spaced ring bonds having a plurality of separate circumferentially spaced grooves opening axially inwardly and extending from the radially inner faces of the bonds in a generally radial direction partially through the material of the bonds to form blade retaining pockets. the axially outer portions of the grooves having greater peripheral width than the axially inner portions of the grooves, and a plurality of blade rings-having peripherally thickened end portions seated in said pockets, there being a separate pocket for each end portion of each blade and each of said end portions substantially fillin out a separate pocket.

3. A blade ring fbr radial flow elastic fluid turbines comprising two axially spaced ring bonds having a plurality of separate circumferentially spaced dovetail grooves opening axially inwardly and extending from the radially inner faces of the bonds in a generally radial direction partially through the material of the bonds to form blade retain 4. A blade ring for radial flow elastic fluid turbines comprising two axially spaced ring bondshaving a plurality of separate circumferentially spaced dovetail grooves opening axially inwardly and extending from the radially inner faces of the bonds in a generally radial direction partially through the material of the bonds to form blade retaining pockets, and a plurality of blades having peripherally dovetail'end portions seated in said pockets, said ring bonds having portions extending axially inwardly at the radially inner ends of each pocket forlocking the blades in the pockets.

5. A blade ring for radial flow elastic fluid turbines comprising two axially spaced ring bonds having a plurality of separate circumferentially spaced grooves opening axially inwardly and extending from the radially inner faces of the bonds in a generally radial direction partially through the material of the bonds to form blade retaining pockets,

and a plurality of blades having end portions seated in said pockets, there being a separate pocket for each end portion of each blade direction partially through the material of V the bonds to form blade retaining pockets,

and a plurality of blades having end ,por-

tions seated in said pockets, there being a sep- I arate pocket for each end portion of each blade and each of said end portionssubstantially filling out a separate pocket, said ring bonds having portions extending axially inwardly at the radially inner'ends of each pocket for locking the blades in the pockets.

In testimony whereof we afiix our signatures.

ERIK OTTO ERIKSSON. GUSTAV NORDGREN.

and each of said end portions substantially filling out a separate pocket, the radially 

